1. Field of the Invention
This invention relates to a semiconductor laser array device having a plurality of striped channels.
2. Description of the Prior Art
Semiconductor laser devices which are useful as light sources for optical discs, optical information processing systems, etc., are required to produce high output power. However, conventional semiconductor laser devices having a single-lasing filament structure can only produce as low as several tens of mW output power.
In order to produce high output power, semiconductor laser array devices, in which a plurality of semiconductor laser devices are disposed in a parallel manner to achieve an optical phase coupling between the adjacent lasing filaments, have been proposed. However, these semiconductor laser array devices cannot attan a 0.degree.-phase shift between the adjacent lasing filaments in the range of a high output power level.
Experimental data of the inventors indicate that although a Fabry-Perot semiconductor laser array device having three striped channels as lasing filaments attains a 0.degree.-phase shift between the adjacent lasing filaments up to a 20 mW output power as shown in FIG. 3, it cannot attain a 0.degree.-phase shift in a range of higher output power. FIG. 4 indicates that the longitudinal mode of this Fabry-Perot semiconductor laser array device in the range of higher than a 20 mW output power is composed of the main mode and two submodes at the shorter wavelength side of the main mode. The temperature of the center striped channel rises more than that of each of the two outer striped channels as the amount of injection electric current into the laser array device is increased. As the temperature of a semiconductor laser rises, in general, the width of the forbidden band therein becomes smaller and the wavelength of the laser light emitted therefrom becomes longer. Thus, it can be said that the abovementioned main mode indicates a laser light derived from the center striped channel, while the two submodes at the shorter wavelength side of the main mode indicate laser lights which are oscillated, respectively, from the outer striped channels without being synchronized with the laser light from the center striped channel.